The manufacture of cheeses or cheese base materials from milk through preparation of a retentate by removal of salts, lactose and water has been taught in various patents and literature references. For example, a patent to Coulter, et al., entitled "Cheese Manufacture from Molecular Sieved Milk," issued Oct. 26, 1976, U.S. Pat. No. 3,988,481, teaches the preparation of cheese from milk which has been de-lactosed and de-watered by a process involving molecular sieving a standardized milk to substantially separate and remove lactose and water-soluble minerals from the milk to render the milk substantially sugar-free, and adding a curd-forming agent to produce curd. The resulting curd is subjected to conventional handling without substantial syneresis to produce a cheese, and molded to a desired form.
A patent to Stenne, entitled "Method for the Manufacture of Cheeses," issued Aug. 12, 1975, U.S. Pat. No. 3,899,596, discloses a process for the production of cheese which comprises treating milk by ultrafiltration to obtain a product having at least some of the protein constituents of the milk, renneting the liquid product after inoculation with suitable ferments, and introducing a batch of the renneted liquid into a vertical chamber in which it is left to coagulate. The coagulum is cut into slabs which provide the end product cheese.
A patent to Maubois, et al., entitled "Manufacture of Cheese from Ultrafiltered Milk," issued Oct. 21, 1975, U.S. Pat. No. 3,914,435, teaches cheese made from heat-treated milk and without conventional draining of whey by a process which involves ultrafiltering of the milk to produce a concentrate having essentially the composition of cheese produced by conventional whey draining processes. The process enables the milk, after ultrafiltration, to be heat-treated without making the milk more difficult to coagulate with rennet, which difficulty normally occurs when milk is heated to high temperatures.
A patent issued to Wargel, et al., entitled "Process and Products from the Manufacture of Cheese-flavored Products," issued June 13, 1981, U.S. Pat. No. 4,244,971, teaches the manufacture of cheeses and process cheese, from ultrafiltered milk.
A patent entitled "Process for Preparing Cheese base," issued Aug. 30, 1983, to Rubin, et al., U.S. Pat. No. 4,401,679, discloses a process for preparing cheese base by concentrating milk through ultrafiltration, combined with diafiltration and evaporation, wherein the retentate from the ultrafiltration is inoculated with an acid culture before evaporation, and after evaporation acidification proceeds to completion in packing.
Further, cheese base material has been taught by evaporating moisture from retentate under turbulent conditions to provide a lower moisture condition. Such a process is described in an article by Ernstrom, et al., entitled "Cheese base for Processing: A High-yield Product from Whole Milk by Ultrafiltration," published in the Journal of Dairy Science, volume 63, 228-234 (1980). The article teaches a process wherein whole milk of normal pH, or acidified to a pH of 5.7, is concentrated by ultrafiltration to about 40 percent of the original milk weight and diafiltered at constant volume until a desired ratio of lactose to buffer capacity is established. Then the retentate is further concentrated by ultrafiltration to 20 percent of the original milk weight. The retentate is then inoculated with cheese starter and incubated to completely ferment the residual lactose, pH control being achieved by controlling the level of lactose from the diafiltration step of the process. The product is further concentrated in a swept-surface vacuum-pan evaporator or a Luwa evaporator. It is pointed out that the use of a batch evaporator is necessitated when the retentate, upon fermentation, curdles or coagulates, since such a product cannot be readily processed in any continuous-flow evaporator.
It is known to add salt during fermentation to prevent coagulation and this was understood many years ago. See: LeLait/November-December, 1974/No. 539-540. Further, it has been disclosed that salt in the retentate may facilitate evaporation as disclosed in an Australian Application, which is the subject of a published application under the Patent Cooperation Treaty W082/01806, published June 10, 1982.
However, the prior art teaches that addition of rennet or other coagulating enzymes to high-solids milk systems causes rapid coagulation, a condition to be avoided during evaporation, as indicated above, since the evaporation is highly inefficient after coagulation occurs. On the other hand, the presence of coagulating enzymes may be desired, particularly in higher-solids cheese, to provide the conventional presence of para kappa casein. The kinetics of enzymatic coagulation of milk is disclosed by Alfred Carlson, in a thesis published in 1982, at the University of Wisconsin, entitled "The Kinetics of Enzymatic Coagulation of Milk."
In the conventional making of cheese with rennet, the macro peptides formed by rennet action are lost in the whey with consequent reduction in yield and loss of nutritious milk protein material. Accordingly, it would be desirable to enjoy the benefit of rennet action while avoiding whey removal with consequent loss of macro peptides.
Further, prior art methods for making cheese base materials at higher-solids with evaporation, in which evaporation is effected with high turbulence or the cheese base material is recovered with substantial working after evaporation, has resulted in destabilization of the higher-solids cheese base material, and a body and texture unlike various cheeses. This destabilization is particularly noticeable at total solids in excess of about 60 to 62 percent, e.g., a cheese such as cheddar cheese, but is also present at solids as low as 55 percent. Accordingly, cheese base materials heretofor produced by evaporating retentates to a total solids in excess of 60 percent hve not provided the typical body and texture characteristics of high-solids cheeses.
In addition, the use of high turbulence throughout evaporation or working after evaporation does not provide a product having a likeness to curd. Prior art methods for making cheese from retentates with evaporation techniques do not disclose a method for making a curd-like product.
The prior art teaches many different steps in respect to the manufacture of cheeses and cheese base materials from milk retentates. Evaporation of milk retentates is a previously known technique, but the resultant product does not have curd character, nor does it convert to a product having the body and texture of cheese. Also, much of the prior art is directed toward the manufacture of higher moisture or soft cheeses, and it has not been directed toward the production of high-solids cheeses from retentates by means of evaporation of retentates. The difficulty which occurs with turbulence at higher-solids, i.e., above 55 percent total solids, is that the product destabilizes and exudes fat, and high-solids product, i.e., above 60 percent total solids, does not have the characteristic cheese body and texture. If the moistures are high enough, fat exudation can be avoided and the body and texture of soft cheeses can be provided.
While, as before indicated, the addition of milk clotting or coagulating enzymes to retentates has been known, such addition has generally been made with concurrent formation of a coagulum which cannot be readily subjected to evaporation, and which is destroyed by turbulence and/or working. The addition of milk clotting enzymes, without coagulation, prior to an evaporation step has not been disclosed. Again, there is not provision in the prior art of a stable high-solids cheese base material or cheese made from an evaporated retentate and having the body and texture of conventionally made cheese.
Accordingly, despite the many teachings of the prior art relating to the manufacture of cheese base material and cheese from retentates derived from milk, there has been a serious lack of a process for producing curd from an evaporation step and high-solids cheese which is stable and which can have the body and texture of American-type cheese.
For purposes of this application, the term "higher-solids cheese" refers to cheeses which have a total solids in excess of 55 percent, whereas the term "high-solids cheeses" is used to refer to those cheeses which have a solids content in excess of 60 percent, and such cheeses are commonly referred to in the trade as hard cheeses. The cheeses having between 55 percent and 60 percent total solids are referred to herein as "semi-soft cheeses." Also for purposes of this application, the term "milk" is meant to include raw whole milk, skim milk, and milk which has been standardized and which may have been pasteurized, clarified, and/or subjected to other appropriate treatment processes.
It is a principal object of this invention to provide a curd and cheese from a retentate by means of evaporation techniques, the curd having knitting characteristics and the cheese having a typical cheese body and texture characteristics.
A further object of this invention is to provide a higher-solids cheese which is stable and does not oil-off, and is manufactured by processing a milk retentate with evaporation techniques.
Another object of this invention is to provide a curd and cheese in which there is formed a substantial percentage of para kappa casein in a process using continuous evaporation methods and equipment.
Still another object of the invention is to provide a process for the manufacture of curd and cheese in which the milk proteins have been subjected to the action of a milk clotting enzyme but which process avoids loss of macro peptides.
A still further object of this invention is the provision of a curd and cheese, made with evaporation of a retentate, which can be pressed and cured like cheese in conventional processes.
Still further objects and advantages of the invention will become apparent by reference to the following description.